Update Automated Power Systems On The Fly
Many facilities require reliable power-control systems to keep HVAC, lighting, and critical equipment running at all times. Replacing outdated control systems is not always the most effective approach.
Douglas H. Sandberg
Prime, emergency, and standby on-site power systems that are more than 10 years old may be outdated and even incapable of providing adequate power to automated systems and conventional power loads that must operate around the clock. Why is that, considering that engine-generator sets and power-transfer switching mechanisms are so durable? There are a number of reasons.
Foremost is that equipment controls become obsolete comparatively quickly. While engine-generator technology has remained fairly consistent, controls have evolved from bulky electromechanical relays to basic transistors and now to programmable logic controllers (PLCs).
Today’s controllers offer tremendous flexibility for designers, owners, and those who maintain them. The control logic remains pretty much the same as with relays, but changes and updates are made within a software program. There’s no need to add relays, timers, or to re-wire components. PLCs are faster, offer greater functionality, and are more precise and reliable than previous control technologies.
Exponential advances in control technology are the primary reason controls become obsolete relatively quickly. The result is an on-site power system that uses a mix of durable machinery (engine-generators, fuel systems, ventilation systems, and load banks) and controls that are subject to premature obsolescence.
This situation creates real problems for building managers, hospital engineers, consultants, and anyone else charged with maintaining life-sustaining infrastructures. It’s a dichotomy and raises a serious question: What can you do?
The first step is to understand the three basic control groups of an on-site power system:
- Sensory inputs. These are sensors that monitor oil pressure, coolant and exhaust temperature, and fuel supply.
- The brain. This is a central controller, such as a PLC, that acts on sensory inputs.
- Active and passive outputs. An active output shuts down an engine when oil pressure drops below a pre-set limit. A passive output turns on an indicator light or sends an alert.
Besides engine-generators, two other systems are required for on-site, power-transfer switches and monitoring and control capabilities.
Automatic transfer switches
Automatic transfer switches also have experienced some of the same issues as engine generators. The switching mechanism has remained durable over many years, while advances in technology have greatly improved control technology. The transfer switch is the system that makes it possible to transfer loads from one power source to another. Without it, on-site power systems as we know them today would not exist.
There are four types of workhorse transfer switches: open transition, closed transition, delayed transition, and soft load.
The open-transition transfer switch breaks from one power source before it connects with another.
The closed-transition transfer switch also breaks from the utility, or normal, source when power fails before connecting to on-site power. When utility power returns, however, this transfer switch transfers loads back to utility power before it breaks the connection with on-site power. This ensures continuous power to critical loads.
The delayed-transition transfer switch delays load transfers to allow large electrical fields, associated with large inductive loads, to collapse before connecting with another power source. This limits potentially damaging in-rush current.
The soft-load transfer switch enables both normal and on-site active power sources to be simultaneously connected to loads. By paralleling the normal, or utility, source and the on-site power source, loads can be “walked” from one source to the other by increasing or decreasing engine-generator loading.
These transfer switches also are available with bypass isolation capability. A manual transfer switch is integrated with the automatic transfer switch, which allows the automatic transfer switch to be taken off line for maintenance while still protecting critical loads.
Monitoring and control capabilities
Advances in technology and computers, and the advent of the Internet, make it possible to be thousands of miles away, yet still monitor the operation of your critical system and, in some cases, control it as well. Controls may be managed with a PC, laptop, or PDA-type device.
Today, real-time monitoring, trending, and management of critical systems are realities from just about anywhere in the world. The ease of operation, flexibility, and functionality offered by current monitoring and control technologies are very tempting. But do they justify replacing an entire on-site power system?
To determine that, you need to answer some basic questions:
- Is my system suitable for current and growing needs? First, distinguish between “wants” and “needs.” Capacity, redundancy, flexibility, load management, and point of control are examples of needs. Type of monitor displays and control options may be examples of wants. Needs dictate the basic system and controls. Wants are options depending on importance and the budget.
- Has my critical load surpassed desired redundancy? Many facility owners and engineers find that on-site power capacity has not kept pace with increased load. Worse yet, the original design may not accommodate additional generator capacity.
- Are my automatic transfer switch loads properly managed? Your engine-generator system must manage loads to prevent overloading available capacity. Loads are divided into blocks and assigned priorities. Highest priority loads are protected and re-powered first in the event of a power failure. The highest priority loads are preserved as long as possible should a generator failure occur. This is an insidious problem as load level and distribution design often changes over the years, so you may end up with a low-priority load on a high-priority automatic transfer switch. This unnecessarily eats up capacity.
- Are my controls up to the task? This could be a difficult question. What is the original operating specification and sequence of operation?
- Is the operation sequence still relevant?
- Do all components still function properly? Several years ago, a major communications link for air traffic failed in New York City due primarily to an alarm which, while functioning, was not working properly and therefore was ignored when there was a real problem. A benchmark functional test, based on the operation sequence, will answer a number of these questions.
- Are replacement components available if a failure occurs? This is key. As systems age and technology advances, components become obsolete and you may not know it. The OEM is, of course, your first stop. However, with the state of business acquisitions, the OEM may now be part of a new group or larger company. In some cases, accurate records of your system may not be available, let alone parts. On-site power systems contain parts not necessarily manufactured by the OEM that designed and manufactured the engine-generator control system or transfer switch. As time passes, those manufacturers will allow components to become obsolete. Your service provider may not have replacement stock.
- Who do you call to service the gear when a problem occurs? This is an age-old debate. You tend to use those who are responsive and offer quality and value, or perhaps someone in your organization has opted for the lowest price. Know which organizations provide important service for your critical systems.
Answering the above questions will draw a good picture of the state of your on-site power system.
Let’s suppose your analysis shows your controls are obsolete, do not function properly, and are not serviceable. Typically, the initial thought will be to replace the outdated gear with a new system. However, the cost of gear and engine-generators alone could range from $250,000 to several million dollars.
This approach, while logical, is fraught with problems. But, let’s say that you have made the case for a necessary investment. Consider these steps.
- Select a partner. Understand the relationships, the interests, and the markup. The key is to use a proven consultant. The firm must understand what you need and offer a good relationship. In short, the right consultant can deliver what you need on time and on budget while protecting your interests.
- Manage order entry and lead time. Understand the process and exercise due diligence. Managing order entry, specification development, vendor selection, and establishment of a schedule is a formidable process. Understand that lead time for a large system may be 14 to 20 weeks.
- Add to the base cost of replacement gear the cost for electrical and mechanical work, in addition to modifications required to decommission the old gear and install the new gear. Depending on the situation, this work could equal the purchase price of the replacement gear. Rigging is another major cost when replacing a large system. Following the disconnection of the old gear, it must be removed. Again, depending on the environment, structural changes over the years, and other physical constraints, this can be another major expense.
- Prepare for operation disruptions. Disruptions are hard, if not impossible, to gauge accurately.
In general, should you take the replacement route, tabulate the known issues and project the cost and consequences. Keep in mind, however, that there will be a large number of “what ifs” and contingencies that must be factored into your equation. At the end of the day, this course of action will be extremely costly in many ways.
A second option is to take the “defend-in-place” approach. Simply stated, this means modernizing the system controls without disrupting facility operations. The defend-in-place strategy is becoming more and more popular as facility owners, engineers, and others analyze the cost of replacement.
In general, it is a faster and less disruptive alternative to replacing an outdated power system, and costs about a quarter of the amount of replacement. This approach has been the option of choice of hospital, data center, and banking facilities nationwide. The defend-in-place process begins by performing the same basic analysis required for a replacement scenario.
Usually, the results show the gear and engine-generators are sound, but the controls are out-dated and some components are no longer supported by the manufacturer. This is perhaps the most common problem.
The solution is to design a custom-control system that typically requires replacing control panels and doors. This approach is minimally invasive and usually allows on-site power systems to remain in service while the outdated sections are modernized one section at a time.
This approach has proven to be a great value to many customers. Retaining engine-generators, fuel systems, radiators, piping, main electrical wiring, gear enclosures, bus, and breakers makes good sense. Updating the control platforms provides modern flexibility, maintainability, and control.
Look at your situation; evaluate the options; get some real numbers; discuss your needs and wants with an experienced service provider. Then decide what’s right for your facility.